• Subject must be 18 years of age or older at the time the Informed Consent is signed

• The subject (or legally acceptable representative if applicable) must provide written informed consent for the trial

• Pathologic diagnosis of prostate cancer of adenocarcinoma histology; presence small cell/neuroendocrine carcinoma is exclusionary

• Metastatic disease as documented by:

‣ Osseous metastases detected by technetium-99m (99mTc) planar bone scan or NaF PET scan, or CT scan at some point in patient's history

⁃ Soft tissue metastases documented on CT or MRI

• PSMA avid metastatic disease as determined by 18F-DCFPyL: at least one lesion with PSMA avidity greater than that of liver (see Prescribing Information for Pluvicto)

• Progressive castration resistant prostate cancer as defined by serum testosterone \< 50 ng/mL and one of the following:

‣ PSA progression confirmed per Prostate Cancer Clinical Trials Working Group (PCWG3)

⁃ Radiographic progression of soft tissues according to Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST 1.1) modified based on PCWG3, or radiographic progression of bone according to PCWG3

• Prior use of a novel AR signaling inhibitor for 4 weeks, including abiraterone acetate plus prednisone/prednisolone, enzalutamide, apalutamide, and/or darolutamide

∙ NOTE: These AR signaling inhibitors may have been used for mCSPC, M0CRPC, and/or mCRPC.

• ECOG PS grade of 0-2

• 10 metastases detectable on molecular imaging (PSMA and FDG PET) and amenable to SBRT

‣ 20% of metastases that are FDG avid but PSMA negative

⁃ Metastases that are not detectable on PSMA and FDG PET do not count toward the total number of metastases, as they are presumed to represent adequately treated sites of disease

• Life expectancy 6 months

• Adequate organ function:

‣ Hemoglobin (hgb) \> 8.0 g/dL

⁃ Absolute neutrophil count (ANC) \> 1500/ µL

⁃ Platelets \> 75,000/ µL

⁃ Total bilirubin 1.5 x ULN OR direct bilirubin ULN for participants with total bilirubin levels \>1.5 x ULN

⁃ ALT and AST 3.0 x ULN ( 5 x ULN for participants with liver metastases) (Child-Pugh class A and B allowed; Child-Pugh class C is excluded)

⁃ Creatinine \< (2.0 mg/dL) during screening evaluation (\>2.0 is allowed if EGFR \>30 mL/min/1.73 m2)

• Subject must agree to use contraception during the treatment period plus an additional 120 days after the last dose of study treatment and must refrain from donating sperm during this period